The paper applies CFD numerical simulation technology, selects the typical urban commercial block as the research object, uses PM I 0 which are from automobile exhausted gas as the source of pollution, simulates the spatial density di stribution of the inhalable pa11icle, verifies the accuracy based on the monitoring data and reveals the diffusion rule of atmospheric pollutants in the three dimensional block space. The results show that there is a close relationship between the diffusion effect of the contaminated gas and three dimensional landscape pattern in blocks. At different height levels such as I 0 meters, 30 meters and 50 meters, the decreasing trend of the density of the pollutants and the uniformity of the spatial distribution are quite obvious. The height of the buildings along the streets, the space combination and the shape of the buildings themselves determine the inner smoothness of the streets. In the urban planning, one must fully consider the effect of three dimensional pattern on air pollution in blocks. From the aspects of urban ventilation, open space, height of the horizon line and disheartened space of the bottom, three dimensional landscape pattern of urban blocks should be optimized, which can effectively improve the current situation of severe atmospheric pollution.